Both raw garlic and a garlic extract called Kyolic have been found to dramatically increase the powers of the immune system's natural killer cells - the first line of defence against infectious disease and perhaps cancer.

Raw or cooked? Garlic has to be raw to kill bacteria and boost immune function. But cooked garlic can lower blood cholesterol and help keep blood thin and perform as a decongestant, cough medicine, mucus regulator and bronchitis preventive. The best advice: eat it both ways.

What about garlic oils, capsules, pills, special preparations? Many of them, warn experts, have none or very little of the active garlic compounds. So you've got to make sure you are getting the best quality products, otherwise you might be wasting your money. In which case, fresh garlic would be best!